It is recommended that you obtain all of the information needed at one time. Using items that are short, concise, clearly written statements that get right to the point will only take seconds to read and rate. A 20 item survey will require only 5 minutes for someone with an 8th grade reading level.
Customer surveys should not contain more than about 30 questions without offering an incentive to compensate participants for their time. It is important to weigh the length and frequency of surveys. Employee surveys may be much longer without impacting response rate or requiring an incentive. A typical employee survey will include approximately 60 questions.